A technique for suppressing or damping vibrations of the vibrating object by absorbing an energy resulting from the vibrations of the vibrating object using a cable or wire attached to the object is widely known in the prior art. For example, Japanese Patent Laid-Open No. 2003-328590 discloses a device for damping vibrations of a hollow tower like structure such as a lamppost or lightning rod. According to the structure with the damping device taught by the Japanese Patent Laid-Open No. 2003-328590, a top end of a cable is fixed to be suspended in a hollow portion of the tower like structure, or a lower end of the cable is fixed in the hollow portion of the tower like structure. Therefore, according to the teachings of Japanese Patent Laid-Open No. 2003-328590, the cable collides against the inner wall of the tower like structure when the tower like structure vibrates so that the vibrations of the tower like structure can be damped.
Japanese Patent Laid-Open No. 2000-353880 discloses a damper comprising an elastic string member to be suspended from an objective structure. Specifically, the string member is a cable made of a plurality of twisted strands. According to the damper for the structure taught by Japanese Patent Laid-Open No. 2000-353880, for example, in case of occurrence of an earthquake, vibrations of the structure can be damped by absorbing energy of an earthquake by the cable. As described, the cable is made of twisted strands. Therefore, according to the teachings of Japanese Patent Laid-Open No. 2000-353880, an optimal damping coefficient can be obtained through friction among the strands resulting from the vibrations and deformations of the cable.
Japanese Utility Model Laid-Open No. 62-143841 discloses a cable vibration damping device, in which an auxiliary wire made of strands having a natural frequency identical to that of a bridge cable is arranged along the bridge cable.
As taught by aforementioned Japanese Patent Laid-Open No. 2003-328590 or Japanese Utility Model Laid-Open No. 62-143841, kinetic energy resulting from vibrations of the moving object is absorbed by the liner material such as a cable or wire made of twisted wire materials attached to a vibrating object, in other words, friction (or frictional heat) is generated inside of the liner material by the kinetic energy. That is, the kinetic energy is converted into thermal energy and the vibration of the vibrating object is thereby damped.
According to the aforementioned conventional vibration damping systems using the wire member, the wire member has to be elongated or thickened to increase a diameter (or a sectional area) thereof in order to damp vibrations more effectively. However, the wire member may be limited to be elongated or thickened. For example, in case of damping vibrations of a transmission case or a transmission cover of a vehicle, the length or the thickness of the wire member has to be limited due to structural constraint of the vehicle, that is, has to be limited within the range not to cause any interference with other components or members when the wire member is vibrated and deformed. For this reason, it is difficult to damp vibrations sufficiently by the conventional vibration damping systems.